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The phrase "increasing the capacity of the frequency inverter" mentioned here refers to the situation where the capacity of the motor used with the frequency inverter is equal to the actual capacity of the motor. Generally speaking, it can be summarized as follows:

01 The rated current of the frequency inverter is too low

As mentioned above, when the rated current of some frequency inverters is less than that of motors of the same capacity, a frequency inverter with a larger range should be selected based on the load conditions of the motor.

02 Motors that may be overloaded for a short period of time

Because the so-called "short time" of an electric motor is relative to the heating time constant. It takes at least a few minutes and at most several dozen minutes. The overload capacity of a frequency inverters is usually 150% for 1 minute. Compared with an electric motor, it is equivalent to having no overload capacity. Therefore, if the motor is likely to operate under overload during the time limit, the capacity of the frequency inverter should be increased.

03 Those who have special requirements for acceleration and deceleration time

The length of the acceleration time of an electric motor is a relative concept related to the magnitude of inertia.

For example, the acceleration time is 5 seconds, which might be too short for a load with a large inertia (large GD2). However, compared with loads with relatively small inertia (small GD2), it might be too long. Generally speaking, for loads that need to start and stop under heavy load, the capacity of the frequency inverter should be considered to be increased in the following situations:

(1) Those that require rapid start and stop; (2) Those with frequent point movements.

04 Those with impact loads

For example, the motor and the load are combined through a clutch. Usually, when the motor has already started rotating, the load also starts to rotate due to the engagement of the clutch. Obviously, at the moment when the clutch is just engaged, the motor's rotational speed will drop, the slip will increase, and the current will also increase, which may cause the overcurrent protection to act. In response to this situation, the capacity of the frequency converter should be increased.